Temperature-stable emulsified fuel

ABSTRACT

The invention provides an emulsified fuel containing a major portion of hydrocarbon liquid and a minor portion of water, containing a set of additives including an emulsifying system comprising from 2.5 to 3.5 parts by weight of at least one sorbitol ester, from 1.5 to 2.5 parts by weight of at least one polyalkoxylated fatty acid ester and from 0.5 to 2.0 parts by weight of at least one polyalkoxylated compound selected from di- and tri-alkylated iso alcohols, the HLB of the emulsifying system varying from 6 to 8.Additive compositions are also provided.

The present invention relates to emulsified fuels which are temperaturestable up to above 70° C. and down to less than −10° C., in particularautomobile fuels intended for use in internal combustion engines. Moreprecisely, the fuels envisaged here contain a major part of a liquidhydrocarbon, and notably:

those of inorganic origin such as petroleum derivatives of the gasoline,gas-oil, kerosene, fuel-oil type and/or such as derivatives of coal orgas (synthetic fuels).

those of vegetable origin such as vegetable oils and esters thereof,

and their mixtures, to which optionally oxygenated compounds such as themono-and poly-alcohols have been added.

The present invention more specifically covers the composition of thefuels constituted by water/liquid hydrocarbon emulsions, preferablywater/Diesel fuel emulsions, that are economically valuable and whichlimit problems of environmental pollution. Below, we shall discussstabilised water/hydrocarbon emulsions, comprising surfactants suitablefor favoring and maintaining the emulsions stable for temperaturevariations between −10° C. and greater than 70° C.

Water very quickly appeared to be a valuable additive or partialsubstitutuent for gasoline or Diesel fuel, as it is inexpensive andnon-toxic, allowing reduction of specific fuel consumption and emissionof poluants whether visible or not.

Despite all these presumed advantages, very few water/hydrocarbon fuelshave been produced industrially and distributed on a wide scale to fuelconsumers.

Among all the tests carried out, it has been envisaged to provide forseparate storage of water and automobile fuel on the vehicle, for mixingprior to injection into the running engine. This approach required acomplex and sophisticated device for mixing and metering out eachcomponent of the mixture to be implemented on board the vehicle. Itbecame clear that the cost, bulk and fragility of such devices madedevelopment of this approach completely dissuasive.

A second approach consisted in storing the pre-metered mixture of waterand fuel, but the distributor soon encountered problems of stabilityduring storage of such mixtures in the temperature ranges varying from−20° C. to 70° C., and the automobile owner met with the problems ofstability of this mixture in the gasoline tank.

Consequently, numerous fruitless technical propositions exist which invain set out to provide emulsified fuels comprising water and, moregenerally, new and non-polluting fuels, leading to a low specificconsumption.

As illustration of this state-of-the-art, we can cite French Patentapplication 2,470,153 which discloses an emulsified fuel, comprisinghydrocarbons, and water, and alcohol (methanol, ethanol) and anemulsifying system formed by sorbitan mono-oleate and by ethoxylatednonylphenol. The concentration of the emulsifying system in the emulsionis comprised between 3 and 10% by volume. The indispensable presence ofalcohol in this emulsion, constitutes an extremely penalizing element,notably in view of the economies and engine performance obtainable withthis emulsion. Additionally, it should be noted that the stability ofthis water-alcohol/hydrocarbon emulsion has not demonstrated itseffectiveness. Indeed, after 72 hours storage of the emulsion,corresponding to a realistic period of non-use of a vehicle operatingwith this fuel, signs of phase separation (dephasing/demixing) can beseen between the hydrocarbons and the hydro-alcoholic mixture. Thede-phased (separated) hydrocarbons at the end of this period can make upup to 3 percent by volume of the emulsion. One can readily imagine thatafter a few days storage, phase separation of the emulsions in Frenchpatent application 2,470,153 will be sufficiently great to make themunsuitable for use, under normal conditions of application.

Additionally, from U.S. Pat. No. 4,877,414, an emulsified fuel is knownthat includes a certain number of additives, including an emulsifyingsystem formed by a sorbitan sesquioleate, sorbitan mono-oleate, andpolyoxyethylene (6 EO) ether of dodecylalcohol. Preferably, according tothat patent, total concentration of all additives is around 2.1 percent.Apart from the emulsifying system, the other additives able to beemployed can be: a mono-α-olefin (decene-1), methoxymethanol, toluene,and alkyl benzene and calcium hydroxides. This formula is extremelycomplex, if only in view of the number of additives employed. It isadditionally relatively expensive. Finally, the emulsified fuelaccording to that patent also itself suffers from a lack of stability,particularly at low temperatures. Applicant has further clearly broughtthis to light by reproducing the preferred example of implementation ofthe emulsified fuel according to this U.S. patent. It was found that theemulsion separated (suffered phase separation) in one hour. Thephenomenon is further accentuated at low temperature, below 5° C. Onecould hardly dare imagine what could happen in an automobile gasolinetank containing this emulsion under strong winter conditions.

The abstract of Japanese Patent 77-69909 given in Chemical Abstracts 87:138513 x, relates to an emulsified fuel (kerosene:water) comprisingsorbitan sesquiolate and polyethylene glycol ether of nonylphenol asemulsifiers. The size of the dispersed aqueous phase is ≦20 μm and, onaverage, is of the order of 10 μm. This technical proposition also doesnot provide a suitable way of satisfying the objectives ofphysico-chemical stability, limitation of pollution, economy andreduction of fuel consumption. That technical teaching consequently inno way helps the skilled person in his investigative work on thisinvention.

A further Chemical Abstract No. 101: 57568 z, summarizing BrazilianPatent 82 4 947 covers an emulsified fuel comprising hydrocarbonsconstituted by extremely viscose and heavy petroleum derivatives, water,ethanol and an emulsifier constituted by ethoxylated nonylphenol. Thisemulsified fuel is intended for use in ovens, conventional fuel oilburners. This fuel could not meet the expected performancespecifications for combustion, pollution limitation and low consumptionin light or heavy vehicle internal combustion engines. Additionally,this emulsion has poor physico-chemical stability.

International application WO 97/34969, in the name of the applicant,discloses emulsified fuels which the present invention sets out toimprove.

These emulsified fuels, which can be automobile fuels, comprise specificamounts of hydrocarbon and a minor amount of a set of additivesincluding, notably, an emulsifying system comprising at least onesorbitol ester, at least one polyalcoxylated fatty acid ester of HLBgreater than or equal to 9, and at least one polyalcoxylated alkylphenolof HLB comprised between 10 and 15, the respective concentration ratiosof these components varying from 2.5-3.5; 1.5-2.5; 0.5-1.9. Thedispersed phase of these emulsified fuels is constituted by waterpresent in an amount of 5-35% by weight while the additives are presentin amount of 0.1 to 2% by weight. These fuels are particularly stableover storage times of at least three months. Nevertheless, it has beennoted that when used in vehicles in which the fuel gets heated up prioror during the injection phase, before introduction into the carburettor,and when a portion is sent back to the gasoline tank after passagethrough a filter reaching temperatures close to 75° C., the emulsifiedfuel separated out into two water and hydrocarbon phases. Thus, a buswhich had been stopped over the weekend could not start again on theMonday morning, all of the fuel having decanted. This decantationphenomenon of the emulsified fuels is accentuated when a high-pressuresupply system is used, favoring temperature increase. In particular, inall the new direct injection diesel engine technologies equipping allnew heavy goods vehicles and an increasingly large percentage of newlight vehicles, fuels are heated to a temperature greater than 70° C.

The performance of these known emulsified fuels, in terms of temperaturestability towards temperatures greater than 75° C. and also at −20° C.can most certainly be improved to provide answers to the problemsassociated with their use under real conditions in a vehicle.

The present invention provides an emulsified fuel that is stable for atleast four days at more than 70° C., fuel stability when cold, in otherwords at −10° C. or, yet again, during storage at up to 40° C. beingmaintained over at least three months without untimely decantation.Additionally, the invention sets out to obtain an emulsified fuel whichmeets all government requirements as regards the environment. Thus, thisinvolves, in particular, replacing the polyalcoxylated alkylphenols usedin numerous emulsified fuels but which are not accepted by alladministrations, by a compound or mixture of compounds which allow notonly the same stability during storage for the emulsion to be obtainedbut which also provides improved stability at a temperature greater than70° C., and also good stability in use over a simulated cycle between−10 and +20° C.

The present invention consequently provides an emulsified fuelcontaining a major portion of hydrocarbon liquid and a minor portion offrom 5 to 35% by weight water, containing a set of additives includingan emulsifying system comprising:

i) from 2.5 to 3.5 parts by weight of at least one sorbitol ester offormula (I) below:

in which the radicals X are identical or different and each correspondto a group selected from OR₁ groups, R₁ being hydrogen or an aliphaticradical having 1-6 carbon atoms, and a R₂—COO— group where R₂ ishydrogen or a linear or branched, saturated or unsaturated aliphatichydrocarbon radical, optionally substituted by at least one hydroxylatedgroup and having 6-22 carbon atoms, at least one X radical correspondingto R₂—COO—,

ii) from 1.5 to 2.5 parts by weight of at least one polyalkoxylatedfatty acid ester of formula (II) below:

in which R₃ is a linear or branched, saturated or unsaturated aliphatichydrocarbon radical, optionally substituted by at least one hydroxylatedgroup and having from 6 to 22 carbon atoms, R₄ is a linear or branchedalkylene group having from 1 to 10 carbon atoms, preferably 2 to 3carbon atoms, n is an integer greater than or equal to 6, preferablyvarying between 6 and 30, and R₅ is hydrogen, a linear or branched alkylgroup having 1 to 10 carbon atoms, or is:

R₆ being identical to or different from R₃,

iii) from 0.5 to 2.0 parts by weight of at least one polyalkoxylatedcompound of general formula (III) below;

in which R₉ and R₁₀ are identical or different, linear or branchedalkylene groups having 1-20 carbon atoms, R₇ is linear or branchedalkylene having 1 to 10 carbon atoms, preferably 1 to 3 carbon atoms, R₈is selected in the group consisting of hydrogen, linear or branchedalkylene groups having 1 to 10 carbon atoms, and

R₁₁ being a linear or branched, saturated or unsaturated aliphaticradical, optionally substituted by hydroxylated functions and having6-22 carbon atoms, m and p are integers varying respectively from 0-20and from 3-10,

the HLB of the emulsifying system varying from 6 to 8.

It has been noticed that, unexpectedly, introducing the compound offormula (III) in combination with the mixture of compounds of formula(1) and formula (II) considerably increased stability of emulsified fuelwhen the latter was maintained for more than three days, orsporadically, at temperatures greater than 50° C. and even greater than75° C., compared to the closest prior art constituted by Internationalapplication WO 97/34969. In effect, the emulsion as implementedpreviously does separate into two phases as soon as the emulsion isbrought to more than 50° C. for more than 24 hours.

In parallel, stability in use and stability during storage of theemulsions according to the invention are maintained, compared to thestate-of-the-art.

Such temperature stability greater than three days is obtained byintroducing the emulsifying system at a concentration of at the most 2%by weight into the emulsified fuels. Obviously, it is always possible tointroduce more emulsifying system into the fuel, but this is notnecessary.

Among the compounds of formula (I), the preferred sorbitol esters arechosen from sorbitol oleates alone or in a mixture, sorbitolsesquioleate being preferred.

The fatty acid esters of formula (II) are selected from oleates,stearates and ricinoleates of polyethylene glycol. The preferred estersare those in which the polyethylene glycol fraction has a molecularweight less than or equal to 600, and preferably less than 450.

The polyalkoxylated compounds of formula (III) which ensure, incombination with the two other components of the emulsifying system, hotfuel stability, are chosen from di- and tri-alkylated iso alcohols, eachalkyl radical having 1-15 carbon atoms, preferably from alcohols thealkyl radicals of which comprise from 5 to 12 carbon atoms. Preferably,they are chosen among iso tridecylic alcohols comprising from 3-10ethoxylated groups.

In the present invention, the hydrocarbonated liquid constituting themajor proportion of the fuel is chosen from the group consisting ofgasolines, medium distillates, synthetic fuels, animal or vegetableoils, whether or not esterified, and mixtures thereof.

The emulsified fuel according to the invention additionally comprises,apart from the hydrocarbon phase, water and the emulsifying system,further additives such as cetane-improvers preferably chosen fromperoxides and/or nitrates and mixtures thereof, and, optionally, ametallic catalyst for soot post-combustion, said metal being one ofthose of the group constituted by magnesium, calcium, cerium, copper,iron or mixtures thereof. It can contain, further, a biocide, preferablya bactericide and/or a fungicide, and also an anti-freeze, in theaqueous phase.

For use as an emulsified fuel, the fuel according to the invention cancontain usual additives such as filterability additives, cloud pointimprovers, lubricity and anti-sedimentation additives, anti-wear agents,anti-foaming agents, anti-corrosion agents, detergent additives, and/oradditives or additive compositions for improving cold flow properties.

Among these additives, we can particularly mention:

a) cetane-improver additives, notably (but not in a limiting way) chosenfrom alkyl nitrates, preferably 2-ethyl hexyl nitrate, aryl peroxides,preferably benzyl peroxide, and alkyl peroxides, preferably ter-butylperoxide.

b) filterability additive, notably (but not in a limiting way) chosenfrom ethylene/vinyl acetate (EVA) copolymers, ethylene/vinyl propionate(EVP), ethylene/vinyl ethanoate (EVE), ethylene/methyl methacrylate(EMMA), and ethylene/alkyl fumarate. Examples of such additives aregiven in European Patent application 0187488, French Patent 2,490,669,European patent applications 0722481, and 0832172.

c) anti-foaming additive, notably (but not in a limiting way) chosenfrom polysiloxanes, oxyalkylated polysiloxanes, and fatty acid amides ofvegetable or animal oil origin. Examples of such additives are given inEuropean patent applications 0861182, 0663000, 0736590.

d) detergent and/or anti-corrosion additives, notably (but not in alimiting manner) chosen in the group consisting of amines, succimides,alkenylsuccinimides, polyalkylamines, polyalkyl polyamines andpolyetheramines. Examples of such additives are given in European patentapplication 0938535.

e) lubricity or anti-wear additive, notably (but not in a limiting way)selected in the group constituted by fatty acids and their ester oramide derivatives, notably glycerol mono-oleate and derivatives of mono-and poly-cyclic carboxylic acids. Examples of such additives are givenin: European patent applications 0680506, 0860494, Internationalapplication WO/98 04656, European patent application 0915944, FrenchPatents 2,772,783 and 2,772,784.

f) cloud point additive, notably (but not in a limiting manner) selectedfrom the group consisting of long chain olefin/(meth)acrylicester/maleimide terpolymers and ester derivatives of fumaric/maleicacids. Examples of such additives are given in European patentapplications 0071513, 0100248, French Patents 2,528,051 and 2,528,423,European patent applications 0112195, 0172758, 0271385 and 0291367.

g) anti-sedimentation additive, notably (but not in a limiting way)selected in the group consisting of copolymers of (meth)acrylicacid/alkyl (meth)acrylate amidified by a polyamine, polyamine alkenylsuccinimides, derivatives of phthalamic acid and double chain fattyamine. Examples of such additives are given in European patentapplications 0261959, 00593331, 0674689, 0327423, 0512889 and 0832172.

h) cold flow properties polyfunctional additive chosen in the groupconsisting of olefin-based polymers and alkenyl nitrate as described inFrench patent application serial No. 99. 12549 of 8th Oct. 1999.

The invention also provides a composition of additives for a fuelcontaining essentially an emulsifying system and, optionally, at leastone further additive selected from the compounds of the group consistingof cetane-improvers, combustion and soot combustion catalytic promoters,biocides, anti-freezes, detergents, lubricity additives, anti-wearadditives, anti-foaming additives, anti-corrosion additives andadditives or additive compositions for improving cold (flow) properties.

The examples below are given by way of illustration of the inventionwithout limiting the scope thereof.

EXAMPLE 1

This present example sets out to give the results for stability of theemulsified fuels of the invention, compared to results for the knownart.

There was consequently prepared, using methods described inInternational application WO 97/34969, several emulsions thecompositions of which differed by the composition of their emulsifyingsystem.

For the purposes of comparison, a standard formulation was used for allthe emulsions examined, obtained with a type EN 590 reference dieselfuel:

13% by weight water containing biocide (2% by volume of the diesel fuel)and, optionally, 10% by weight monoethyleneglycol in winter formulations

1% by volume of diesel fuel of an organic biocide

1.86% by weight of an emulsifying system

and 1% by weight of a cetane-improver additive

the remaining percentage by weight being the diesel fuel.

Emulsifying system compositions are given in Table 1 below:

TABLE 1 Surfactant composition A B C D E F F′ G H I J K L M N Sorbitansesquiolate 3 3 1.5 3 3 1.5 1.5 1 3 Sorbitan monooleate 3 3 1.5 1.5 1.51.5 Sorbitan laurate 1.5 Sorbitan stearate 1.5 PEG 300 1 PEG 6E0monooleate 2 2 2 2 PEG 7.4EO monooleate 2 2 2 2 2 2 2 PEG 600 monooleate1 Ethoxylated 1 1 1 1 3 nonylphenol 9EO Ethoxylated 1 nonylphenol 12EOEthoxylated 1 1.5 1.5 nonylphenol 30EO Ethoxylated decylic 1 alcohol 3EOEthoxylated isotridecylic 1 1 1 1 alcohol 7.5EO HLB of emulsifying 7.27.5 7.6 7.6 7.6 7.6 7.6 8.2 10.1 8.1 9.2 9.6 9.6 10.1 7 system

In this table, compositions A, C and F are compositions according to theinvention, compositions B, D, E and N are comparative examples.

Emulsion quality was evaluated on the basis of granulometry, storagestability regardless of ambient temperature, stability in use, stabilityin storage and temperature stability.

By image analysis from micrographs, the homogeneous appearance of thewater droplets dispersed in the continuous diesel fuel phase wascharacterised per their mean particle size and their distribution.

Emulsions stability in use was characterised by an absence ofdemixing/decantation or other breakage of emulsion in a 1 liter beaker,that had undergone a stimulation cycle corresponding to the presumedrecirculation cycle of a diesel fuel in an automobile fuel tank.

By the term stimulating cycle, we mean a temperature cycle consistingin:

bringing a sample down to a temperature of −10° C. over one hour

increasing sample temperature from −10° C. to +40° C. over 1 hour,

and then dropping this temperature to +10° C. over three hours,

finally, bringing the temperature down to −10° C. over 7 hours andkeeping the sample at this temperature for one hour.

We consider that demixing occurs during this stimulating cycle when, atthe end of the cycle, the volume of supernatant liquid, the decanteddiesel fuel, is greater than 5% by volume of the total sample volume or,yet again, when water appears at the bottom of the beaker.

Storage stability is determined by absence of demixing/decantation afterthree months static storage in conical flasks, of three samples kept at,respectively, 0° C., 20° C. and 40° C.

In this case, demixing is characterised by separation into two separatephases which are not necessarily transparent.

Hot stability is characterised by a complete absence ofdemixing/decantation after four days static storage at 75° C.

For this latter stability, demixing is characterised by separation intotwo transparent phases.

Stabilities were evaluated by the extent of time separating preparationof the emulsion and the time demixing/decantation occurred. Depending onstability, this time is measured in hours (h), days (d), weeks (w) andmonths (m).

The complete results are given in Table II below.

TABLE II Composition surfactants A B C D E F F′ G H I J K L M N For-summer summer summer summer summer summer winter summer summer summersummer summer sum- Summer sum- mu- 7% 7% 7% mer mer lation MeOH MeOHMeOH Specific additive Dis- mono mono mono mono mono mono mono poly polypoly poly poly poly poly poly persity 1 μm 1 μm 1 μm 1 μm 1 μm 1 μm 1 μm1-10 1-20 1-20 1-20 1-20 1-20 1-20 1-20 granulo- μm μm μm μm μm μm μm mmmetry (d) Stability yes yes yes yes yes yes yes no no no no no no no noin use Stability in storage  0° C., 4 w 4 w 4 w 1 h 1 h 1 h 1 h 1 h 1 h1 h 2 h 20° C., 3 m 3 m 3 m 3 m 3 m 3 m 3 m 2 w 1 d 1 d 1 d 2 h 2 h 2 h4 h 40° C. 3 m 3 m 3 m 1 d 1 h 1 h 1 h 1 h 1 h 1 h hot 3 w 1 w 3 w 1 w 1w 3 w 2 w 1 h 1 h 1 h 1 h 1 h 1 h 1 h 1 h stability 75° C.

It is seen from this table that stability in use and stability instorage of emulsifying systems A, C, F, and F′ according to theinvention are preserved when compared to emulsifying systems B, D, E andN according to International application WO 97/34969. Temperaturestability is however greatly improved. It is also seen that the twoformulations of the emulsifying systems according to this presentapplication and to International application WO 97/34969 are much betterthan formulations G to M.

What is claimed is:
 1. An emulsified fuel containing a major portion ofhydrocarbon liquid and a minor portion of from 5 to 35% by weight water,containing a set of additives including an emulsifying systemcomprising: i) from 2.5 to 3.5 parts by weight of at least one sorbitolester of formula (I) below:

in which the radicals X are identical or different and each correspondto a group selected from OR₁ groups, R₁ being hydrogen or an aliphaticradical having 1-6 carbon atoms, and a R₂—COO— group where R₂ ishydrogen or a linear or branched, saturated or unsaturated aliphatichydrocarbon radical, optionally substituted by at least one hydroxylatedgroup and having 6-22 carbon atoms, at least one X radical correspondingto R₂—COO—, ii) from 1.5 to 2.5 parts by weight of at least onepolyalkoxylated fatty acid ester of formula (II) below:

in which R₃ is a linear or branched, saturated or unsaturated aliphatichydrocarbon radical, optionally substituted by at least one hydroxylatedgroup and having from 6 to 22 carbon atoms, R₄ is a linear or branchedalkylene group having from 1 to 10 carbon atoms, n is an integer greaterthan or equal to 6, and R₅ is hydrogen, a linear or branched alkyl grouphaving 1 to 10 carbon atoms, or is:

R₆ being a linear or branched, saturated or unsaturated aliphatichydrocarbon radical, optionally substituted by at least one hydroxylatedgroup and having from 6 to 22 carbon atoms, iii) from 0.5 to 2.0 partsby weight of at least one polyalkoxylated compound of general formula(III) below;

in which R₉ and R₁₀ are identical or different, linear or branchedalkylene groups having 1-20 carbon atoms, R₇ is linear or branchedalkylene having 1 to 10 carbon atoms, R₈ is selected in the groupconsisting of hydrogen, linear or branched alkylene groups having 1 to10 carbon atoms, and

R₁₁ being a linear or branched, saturated or unsaturated aliphaticradical, optionally substituted by hydroxylated functions and having7-22 carbon atoms, m and p are integers varying respectively from 0-20and from 3-10, the HLB of the emulsifying system varying from 6 to
 8. 2.The fuel according to claim 1, characterised in that emulsifying systemconcentration is less than or equal to 2% by weight.
 3. The fuelaccording to claim 1, characterised in that the sorbitol esters offormula (I) are chosen from sorbitan oleates alone or in mixture.
 4. Thefuel according to claim 2, characterised in that the sorbitol esters offormula (I) are chosen from sorbitan oleates alone or in mixture.
 5. Thefuel according to claim 1, characterised in that the fatty acid estersof formula (II) are chosen from oleates, stearates and ricinoleates ofpolyethyleneglycol, the esters optionally being those of which thepolyethyleneglycol fraction has a molecular weight less than or equal to600.
 6. The fuel according to claim 2, characterised in that the fattyacid esters of formula (II) are chosen from oleates, stearates andricinoleates of polyethyleneglycol, the esters optionally being those ofwhich the polyethyleneglycol fraction has a molecular weight less thanor equal to
 600. 7. The fuel according to claim 1, characterised in thatthe polyalkoxylated compounds of formula (III) are selected from di- andtri-alkylated iso alcohols, each alkyl radical having 1-15 carbon atoms.8. The fuel according to claim 2, characterised in that thepolyalkoxylated compounds of formula (III) are selected from di- andtri-alkylated iso alcohols, each alkyl radical having 1-15 carbon atoms.9. The fuel according to claim 8, characterised in that thepolyalkoxylated compounds of formula (III) are isotridecylic alcoholshaving 3-10ethoxylated groups.
 10. The fuel according to claim 1,characterised in that the sorbitol esters of formula (I) are chosen fromsorbitan oleates alone or in mixture; the fatty acid esters of formula(II) are chosen from oleates, stearates and ricinoleates ofpolyethyleneglycol, the esters optionally being those of which thepolyethyleneglycol fraction has a molecular weight less than or equal to600; the polyalkoxylated compounds of formula (III) are selected fromdi- and tri-alkylated iso alcohols, each alkyl radical having 1-15carbon atoms.
 11. The fuel according to claim 2, characterised in thatthe sorbitol esters of formula (I) are chosen from sorbitan oleatesalone or in mixture; the fatty acid esters of formula (II) are chosenfrom oleates, stearates and ricinoleates of polyethyleneglycol, theesters optionally being those of which the polyethyleneglycol fractionhas a molecular weight less than or equal to 600; the polyalkoxylatedcompounds of formula (III) are selected from di- and tri-alkylated isoalcohols, each alkyl radical having 1-15 carbon atoms.
 12. The fuelaccording to claim 1, characterised in that the hydrocarbon liquid isselected in the group consisting of gasolines, middle distillates,synthetic fuels, animal or vegetable oils whether esterified or not, andmixtures thereof.
 13. The fuel according to claim 10, characterised inthat the hydrocarbon liquid is selected in the group consisting ofgasolines, middle distillates, synthetic fuels, animal or vegetable oilswhether esterified or not, and mixtures thereof.
 14. The fuel accordingto claim 11, characterised in that the hydrocarbon liquid is selected inthe group consisting of gasolines, middle distillates, synthetic fuels,animal or vegetable oils whether esterified or not, and mixturesthereof.
 15. The fuel according to claim 1, characterised in that itcomprises cetane-improver additives, selected from peroxides and/ornitrates and mixtures thereof and, optionally, a metallic catalyst forsoot post-combustion, said metal being one of those of the groupconstituted by magnesium, calcium, barium, cerium, copper, iron ormixtures thereof.
 16. The fuel according to claim 10, characterised inthat it comprises cetane-improver additives, selected from peroxidesand/or nitrates and mixtures thereof and, optionally, a metalliccatalyst for soot post-combustion, said metal being one of those of thegroup constituted by magnesium, calcium, barium, cerium, copper, iron ormixtures thereof.
 17. The fuel according to claim 14, characterised inthat it comprises cetane-improver additives, selected from peroxidesand/or nitrates and mixtures thereof and, optionally, a metalliccatalyst for soot post-combustion, said metal being one of those of thegroup constituted by magnesium, calcium, barium, cerium, copper, iron ormixtures thereof.
 18. The fuel according to claim 1, characterised inthat the aqueous phase contains a biocide, a bactericide and/or afungicide and, optionally, an anti-freeze.
 19. The fuel according toclaim 1, characterised in that it includes one or several filterability,cloud point improving, lubricity, anti-sedimentation, anti-wear,anti-foaming, anti-corrosion, or detergent additives and/or additives orcompositions of additives for improving cold (flow) properties.
 20. Anadditive composition for a fuel, characterised in that it essentiallycontains the emulsifying system as defined in claim 1 and, optionally,at least one further additive selected from the compounds of the groupconsisting of cetane-improvers, combustion and soot combustion catalyticpromoters, biocides, anti-freezes, detergents, lubricating additives,anti-wear additives, anti-foaming additives, anti-corrosion additivesand additives or additive compositions for improving cold (flow)properties.
 21. The fuel according to claim 1, characterised in that R₄is a linear or branched alkylene group having from 2 to 3 carbon atoms.22. The fuel according to claim 1, characterised in that n is an integerfrom 6 to
 30. 23. The fuel according to claim 1, characterised in thatR₇ is a linear or branched alkylene having 1 to 3 carbon atoms.
 24. Thefuel according to claim 3, characterised in that the sorbitan oleatecomprises sorbitan sesquioleate.
 25. The fuel according to claim 4,characterised in that the sorbitan oleate comprises sorbitansesquioleate.
 26. The fuel according to claim 5, characterised in thatthe polyethyleneglycol fraction has a molecular weight less than 450.27. The fuel according to claim 6, characterised in that thepolyethyleneglycol fraction has a molecular weight less than
 450. 28.The fuel according to claim 7, characterised in that the alkyl radicalscomprise 2-12 carbon atoms.
 29. The fuel according to claim 8,characterised in that the alkyl radicals comprise 2-12 carbon atoms. 30.The fuel according to claim 10, characterised in that the sorbitanoleate comprises sorbitan sesquioleate.
 31. The fuel according to claim10, characterised in that the polyethyleneglycol fraction has amolecular weight less than
 450. 32. The fuel according to claim 10,characterised in that the alkyl radicals comprise 2-12 carbon atoms. 33.The fuel according to claim 11, characterised in that the sorbitanoleate comprises sorbitan sesquioleate.
 34. The fuel according to claim11, characterised in that the polyethyleneglycol fraction has amolecular weight less than
 450. 35. The fuel according to claim 11,characterised in that the alkyl radicals comprise 2-12 carbon atoms. 36.The fuel according to claim 20, characterised in that the fuel is amotor fuel.